Hello Spencer and welcome to Seven Forums.
I went to the download link you provided. The SpoutCraft Installer successfully downloaded to my desktop. When I double clicked the installer it opened up the required dialog box asking for my Minecraft login credentials. So it seems to be working on my computer.
Perhaps there was a momentary glitch when you downloaded the client earlier. Try clearing your browser's cache and try again. (Control panel > Internet options > Browsing history.)